Fuel processing systems include a fuel processor and a fuel cell stack. Fuel processors produce hydrogen gas from a feedstock. One type of fuel processor is a steam reformer, which reacts steam with an alcohol or hydrocarbon at an elevated temperature to produce a product stream containing hydrogen gas. The product stream is delivered to the fuel cell stack, which produces an electric current therefrom. This electric current can be used to satisfy the electric load of an associated energy-consuming device, such as a household, vehicle, boat, generator and the like. A byproduct of producing the electric current is heat, which is formed when protons liberated from the hydrogen gas in the anode chamber of a fuel cell react with electrons and oxygen in the cathode chamber to form water.
Besides being able to satisfy the electrical demands of the associated device, the fuel processing system also provides a harvestable source of thermal energy. For example, heat may be harvested from the fuel cell stack directly, or from the exhaust from the fuel cell stack's cathode chamber. If the fuel processor utilizes a combustion region to maintain the processor within selected elevated temperature ranges, the exhaust from this combustion region may also be tapped to harvest thermal energy.
Therefore, a fuel processing system offers several avenues for recovering thermal energy that otherwise would be lost. The present invention provides a system and method for not only recovering thermal energy from the fuel processing system, but also maintaining and controlling the utilization of this recovered thermal energy to meet the thermal loads of one or more associated devices.
Many other features of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which preferred embodiments incorporating the principles of this invention are disclosed as illustrative examples only.